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Showing papers on "Co-channel interference published in 1977"


PatentDOI
TL;DR: In this article, an improved system and method for reducing adjacent channel interference in radio systems by making use of the so-called "cocktail party effect" was proposed. But it is not applicable to the reception of AM Stereo signals but it may also be used to improve the performance of monophonic systems.
Abstract: An improved system and method for reducing adjacent channel interference in radio systems by making use of the so called "cocktail party effect". Also, the selectivity is improved by measuring the level of adjacent channel interference above and below the desired channel and automatically changing selectivity characteristics of the receiver in accordance with the measured interference. The system is particularly applicable to the reception of AM Stereo signals but it may also be used to improve the performance of monophonic systems.

34 citations




Journal ArticleDOI
01 Aug 1977
TL;DR: In this article, the minimum acceptable ratio of RF carrier to interference at the input terminals of receiving equipment, commonly called protection ratios, are dependent upon a multitude of parameters, including the quality of service demanded, receiver characteristics, propagation conditions, the nature of the interference, and the frequency separation between desired and undesired signals.
Abstract: Minimum-acceptable ratios of RF carrier to interference at the input terminals of receiving equipment, commonly called protection ratios, are dependent upon a multitude of parameters. For a given type of radio service, primary considerations are the quality of service demanded, receiver characteristics, propagation conditions, the nature of the interference, and the frequency separation between desired and undesired signals. Representative values used are scattered throughout CCIR and other literature. Cochannel values are gathered together in this paper for convenient reference.

2 citations


Proceedings ArticleDOI
16 Mar 1977
TL;DR: This paper analyzes the extent of TVI due to transmitter operation at 222 to 225 MHz and three approaches are used in the analysis -- theoretical, experimental, and empirical.
Abstract: One of the major factors contributing to the delay in FCC approval of the proposed 220 MHz Class E Citizens Radio Service has been the television interference issue. This paper analyzes the extent of TVI due to transmitter operation at 222 to 225 MHz. Three approaches are used in the analysis -- theoretical, experimental, and empirical. A "radius of interference" is obtained from each approach. Methods of reducing the interference realized are briefly considered.

1 citations


01 Dec 1977
TL;DR: In this article, a computer simulation model for determining the manner in which undesired spread spectrum signals affect the performance of conventional narrowband AM and FM voice communication systems is described, using articulation index as the measure of performance.
Abstract: : A computer simulation model developed for determining the manner in which undesired spread spectrum signals affect the performance of conventional narrowband AM and FM voice communication systems is described. Direct-sequence, frequency-hopping and hybrid, frequency-hopping/direct-sequence, spread spectrum interference signals were modeled. Binary phase-shift keying and minimum-shift keying were included for the carrier modulation of the direct-sequence signals and the direct-sequence portion of the hybrid signals. In addition to the spread spectrum interference, pulsed interference and white Gaussian noise were modeled. Using articulation index as the measure of performance, comparisons are made between system performance for direct-sequence interference and white Gaussian noise. System performance for frequency-hopping or frequency-hopping/direct-sequence interference is compared with that for pulsed interference. (Author)

1 citations


01 Mar 1977
TL;DR: The interference cancellation system unit tested handled up to four interfering transmitters and was found to perform as specified and reduce received interfering signals at power levels up to + 10 decibels referred to 1 milliwatt (dBm) down to at least-45 dBm.
Abstract: : This report describes a device to be used at sites, such as remote center airground facilities (RCAG's) and Flight Service Stations (FSS's) to counteract the interference due to reception of strong signals from collocated transmitters. The interference cancellation system unit tested handled up to four interfering transmitters and was found to perform as specified and reduce received interfering signals at power levels up to + 10 decibels referred to 1 milliwatt (dBm) down to at least-45 dBm. (Author)

1 citations


Journal ArticleDOI
TL;DR: In this paper, the interference from the digital single channel per carrier (SCPC) circuits into frequency-modulated carrier systems has been calculated by convolving the desired and the interfering spectra extending the previously published works.
Abstract: The interference from the digital single channel per carrier (SCPC) circuits into frequency-modulated carrier systems has been calculated by convolving the desired and the interfering spectra extending the previously published works. Resulting interference noise power in FDM/FM systems covering a wide range of modulation indices and basebands has been presnted. Also plots of interference noise power as a function of the number of SCPC circuits have been presented for various values of carrier power to interference power ratios.

1 citations


01 Jul 1977
TL;DR: In this article, the problem of interference in optical communications systems caused by such communication systems is discussed together with suggestions to reduce this interference, and the propagation of optical signals is studied to determine which propagation modes can contribute to interference.
Abstract: : The problem of interference in optical communications systems caused by such communication systems is discussed together with suggestions to reduce this interference. The propagation of optical signals is studied to determine which propagation modes can contribute to interference. Twenty-four modes of possible interference are identified and analyzed. Conclusions are drawn which indicate that in 21 of the 24 modes interference can be eliminated by simple geometric and modulation coordination restrictions. In the three remaining modes, which are scatter links, geometric coordination can resolve the conflicts, but it is definitely more restrictive and difficult to implement than for other modes. (Author)

1 citations


Proceedings ArticleDOI
01 Aug 1977
TL;DR: The past decade has seen increased interest in spread spectrum systems on the part of the United States military services, based primarily on the ability of such systems to operate in the presence of deliberate jamming signals which would render conventional, i.e., narrow-band, systems inoperative.
Abstract: The past decade has seen increased interest in spread spectrum systems on the part of the United States military services, based primarily on the ability of such systems to operate in the presence of deliberate jamming signals which would render conventional, i.e., narrow-band, systems inoperative. Other features of interest in spread spectrum systems which have been exploited in various ways include; the relative immunity of such systems from inadver­ tent interference, the ease with which such systems can provide multiple access communications networks, and for navigation and location purposes the precise timing information which can be derived from systems employing high rates in the spectrum spreading func­ tion. by employing increasingly complex coding procedures the actual rate R may be made to approach the number C as closely as desired.

Proceedings ArticleDOI
01 Aug 1977
TL;DR: In this paper, the frequency/distance-separation (FD) tradeoff curve has been used for analyzing the electromagnetic compatibility between essentially all kinds of spread spectrum (SS) transmitters and narrow-band and wide-band receivers.
Abstract: Spread spectrum (SS) signals usually have rela­ tively low spectral-power densities. The levels of the noise-like responses they produce in narrow-band receivers are tolerable provided the distance separa­ tions and/or the frequency separations between the offending sources and the receivers are sufficient. Attaining sufficient separation in either dimension may be difficult, depending on t h e resources available. An analytical tool that can be used to help assure that these resources will be used as effectively as possible is the frequency/distance-separation (FD) tradeoff curve. This paper presents a brief des­ cription of a procedure for generating FD curves and illustrates several applications of the curves. The procedure is a part of a capability that has been developed recently for analyzing the electromagnetic compatibility fEMC) between essentially all kinds of SS transmitters and narrow-band and wide-band